feat: Implement Zero-Gap Hot-to-Cold Time-Series Migration

backend/src/database/migrations/051_hot_cold_migration_manifest.ts

@@ -0,0 +1,50 @@
+import type { Knex } from "knex";
+
+/**
+ * Migration manifest table for the zero-gap hot-to-cold time-series migration protocol.
+ *
+ * Each row represents one archival segment: a contiguous time range for one entity type
+ * (prices, health_scores, liquidity_snapshots, …).  The manifest is the single source of
+ * truth for migration state, enabling idempotent resume after failure and duplicate-free
+ * cutover.
+ *
+ * Lifecycle:
+ *   pending → migrating → verifying → complete
+ *                     ↘ failed → rolled_back
+ */
+export async function up(knex: Knex): Promise<void> {
+  await knex.schema.createTable("migration_manifests", (t) => {
+    t.uuid("id").primary().defaultTo(knex.raw("gen_random_uuid()"));
+
+    t.string("entity_type", 50).notNullable();
+    t.string("archive_table", 100).notNullable();
+
+    t.timestamp("range_start", { useTz: true }).notNullable();
+    t.timestamp("range_end", { useTz: true }).notNullable();
+
+    // 'pending' | 'migrating' | 'verifying' | 'complete' | 'failed' | 'rolled_back'
+    t.string("status", 20).notNullable().defaultTo("pending");
+
+    t.integer("schema_version").notNullable();
+    t.bigInteger("row_count").nullable();
+
+    // SHA-256 hex of canonical row content — proves archive integrity
+    t.string("checksum", 64).nullable();
+
+    t.text("error_message").nullable();
+
+    t.timestamp("started_at", { useTz: true }).nullable();
+    t.timestamp("completed_at", { useTz: true }).nullable();
+    t.timestamp("created_at", { useTz: true }).notNullable().defaultTo(knex.fn.now());
+
+    // Prevent duplicate manifests for the exact same segment
+    t.unique(["entity_type", "range_start", "range_end"]);
+
+    t.index(["entity_type", "status"], "idx_migration_manifests_entity_status");
+    t.index(["status", "created_at"], "idx_migration_manifests_status_created");
+  });
+}
+
+export async function down(knex: Knex): Promise<void> {
+  await knex.schema.dropTableIfExists("migration_manifests");
+}